This invention relates to a motor vehicle speed control method in which distance to an object in front of the motor vehicle is detected by a distance sensor and supplied to a control unit which generates one or more manipulated variables for controlling the driving speed of the motor vehicle as a function at least of a desired distance from the vehicle to the detected object. The desired distance is determined from at least the instantaneous driving speed and/or a prescribed desired speed. Furthermore, the invention relates to a motor vehicle speed control arrangement which includes a distance sensor for detecting the distance to an object in front of the motor vehicle and a control unit for generating a manipulated variable to control the driving speed of the motor vehicle as a function of at least a desired distance to the detected object which is determined from at least the instantaneous driving speed and/or a prescribed desired speed, and in which it is possible to supply at least the instantaneous driving speed and the distance to an object detected in front of the motor vehicle as actual variables.
U.S. Pat. No. 4,622,636 describes a method and arrangement for automatic motor vehicle speed control in which the driving speed is maintained at a selected speed if no vehicle is driving in front of the controlled vehicle whereas the speed is controlled in accordance with the distance to a vehicle in front if such a vehicle is detected. That patent deals with the problem which arises if a vehicle driving in front which is below a selected speed value suddenly is no longer detected. According to the patent both control functions are disabled if the driving speed is outside a predetermined range around the selected driving speed if there is no vehicle in front, or after a vehicle in front is no longer detected in a monitored region.
U.S. Pat. No. 5,648,905 discloses a distance controller for a motor vehicle by which, after the driving path of the motor vehicle has been determined, a vehicle located in front of the motor vehicle with which the motor vehicle is to dock is detected. Thereafter, the docking operation is performed. If the vehicle in front is no longer detected for any reason, the docking operation is terminated, that is to say the distance controller switches off.
Loss of detection of an object in front of a vehicle can be due to various reasons: the vehicle has initiated an overtaking operation; the road has a bend and the distance sensor does not detect the entire course of the bend; or the detected object has turned off the road. In each of these cases, the speed control must react differently to be acceptable to a driver.